Averages

The query processor AVERAGE field qualifier is widely supported by multivalue
environments but just what does it do?

The default behaviour of the AVERAGE keyword is to accumulate a total of the
value of the field to which it is attached and then report this value divided
by the number of records on the "total" line. If a record has this field empty
or non-numeric, it is treated as zero.

Most spreadsheet tools do not behave this way. If a cell in a column to be
averaged in empty or non-numeric, the normal action is to ignore the cell both
in terms of accumulating the total and also when determining the number of
data items for the division. In QM and many other multivalue products
this behaviour can be enabled by use of the NO.NULLS qualifier.

Alternative Averages

The AVERAGE keyword described above calculates what is usually referred to as
the mean value. There are other ways in which mathematics defines an
average to be calculated.

The median value is defined as the middle value in a sorted list of all
values, including repeated values, in the data being averaged. Where there are
an even number of values, the median value is the average of the two values in
the centre of the list.

The mode value is the most frequently occuring value in the data being
averaged.

In QM, these alternative averaging methods are provided by the MEDIAN and MODE
field qualifiers. Whilst not strictly an average, the related RANGE field
qualifer shows the difference between the minimum and maximum field value. All
three of these field qualifiers support use of NO.NULLS to ignore empty and
non-numeric data.